OBJECTIVES: This study evaluated the effect of camphorquinone (CQ)-amine ratio on the C=C double bond conversion of resins with binary and ternary photoinitiation systems. MATERIALS AND METHODS: Two monomer mixtures (37.5 Bis-GMA/37.5 Bis-EMA/25 TEGDMA) with binary systems (CQ/DMAEMA in weight ratio, group A [0.5/1.0] and B [1.0/0.5]) and four mixtures with ternary system (CQ/OPPI/DMAEMA, group C [0.1/1.0/0.1], D [0.1/1.0/0.2], E [0.2/1.0/0.1] and F [0.2/1.0/0.2]) were tested: 1 : 2 or 2 : 1 CQ-amine ratio in binary system, while 1 : 1 ratio was added in ternary system. The monomer mixture was cured for 5, 20, 40, and 300 sec with a Demetron 400 curing unit (Demetron). After each exposure time, degree of conversion (DC) was estimated using Fourier transform infrared (FTIR) spectrophotometer (Nicolet 520, Nicolet Instrument Corp.). The results were analyzed by ANOVA followed by Scheffe test, with p = 0.05 as the level of significance. RESULTS: DC (%) was expressed in the order of curing time (5, 20, 40, and 300 sec). Group A (14.63 +/- 10.42, 25.23 +/- 6.32, 51.62 +/- 2.69, 68.52 +/- 2.77); Group B (4.04 +/- 6.23, 16.56 +/- 3.38, 37.95 +/- 2.79, 64.48 +/- 1.21); Group C (16.87 +/- 5.72, 55.47 +/- 2.75, 60.83 +/- 2.07, 68.32 +/- 3.31); Group D (23.77 +/- 1.64, 61.05 +/- 1.82, 65.13 +/- 2.09, 71.87 +/- 1.17); Group E (28.66 +/- 2.92, 56.68 +/- 1.33, 60.66 +/- 1.17, 68.78 +/- 1.30); Group F (39.74 +/- 6.31, 61.07 +/- 2.58, 64.22 +/- 2.29, 69.94 +/- 2.15). CONCLUSION: All the monomers with ternary photoinitiation system showed higher DC than the ones with binary system, until 40 sec. Concerning about the effect of CQ-amine ratio on the DC, group A converted into polymer more than group B in binary system. However, there was no significant difference among groups with ternary system, except group C when cured for 5 sec only.
Camphor ; Fourier Analysis ; Polymers

PURPOSE: This study evaluated the depth of cure of resin composite cured by light through a translucent fiber post. MATERIALS AND METHODS: The opaque plastic tubes in various lengths of 2, 4, 6, 8, 10, 12, 14 mm. were filled with resin composite in which two different translucent fiber posts were inserted into the center and photo-polymerized for 40 seconds. The degree of conversion of the cured composite at bottom surface were examined using Fourier transform infrared attenuated total reflection spectrometer (FTIR/ATR) at 0.1, 0.5 and 1.0 mm apart from the post surface. RESULTS: The degree of conversion of the 0.1 mm, 0.5 mm, 1.0 mm apart from the post surface was highest at the 2 mm level and continuously decreased when the distance from the light source was increased and drastically decreased when the depth from the top of the post was greater than 4-6 mm. For each level, the highest degree of conversion was at 0.1 mm from the post surface and decreased continuously when the distance apart from the post surface was increased. CONCLUSION: The quantity of light transmission depends on the type of post and the light transmission capability of the post, especially after 4-6 mm depth and the area further apart from the post surface, are insufficient for clinical light activation of resin composite.
Fourier Analysis ; Plastics

To promote the electrophysiologic diagnostic efficiency, the program for calculation of the total power in the frequency domain and of the area in the time domain of the electroretinogram was designed. The total power is calculated by integration of the squared power spectrum obtained by Fourier transform (Parseval theorem) in the time domain. The dominant power is the power of the dominant frequency in power spectrum and is calculated by integration of the squared peak area spectrum. The sectional inegration of the squared power spectrum can be established by manual input. The inplemented software also has the functions that calculate the summed amplitud and area of the oscillatory potentials in the time domain. And it performs each functions by selection of pop-up menu with mouse to use conveniently under graphic interface, compatible with UTAS-E2000 system.
Animals ; Fourier Analysis ; Mice

PURPOSE: Although it is well known that the pulsatile Doppler waveforms change in shape with disturbed flow, interpretation of the waveforms has largely been subjective. We aimed to describe the Doppler waveforms of the lower extremity objectively by parameters of Fourier transformation. METHOD: Sixty-eight Doppler arterial waves were analyzed in this study. They were classified according to the clinical findings; Group I: no ischemic symptoms with ankle pressure>100 mmHg (N=17). Group II: no ischemic symptoms with ankle pressure 80~100 mmHg (N=18). Group III:symptoms of claudication (N=19). Group IV: rest pain or tissue loss (N=14). The waveforms were Fourier transformed and their amplitudes and phases were compared up to the third harmonics. RESULT: Both the fundamental and second harmonics were predominant in group I. In contrast, fundamental harmonic was predominant with disturbed flow. The phases of the fundamental and second harmonics were delayed with disturbed flow. Relative phase (difference of phase between higher harmonics and fundamental harmonic) tended to be shortened with disturbed flow. CONCLUSION: Abnormal waveforms are characterized by predominant amplitude of the first harmonic, phase delay, and shortening of the relative phase. These parameters may be useful for differentiation of Doppler waveforms.
Ankle ; Fourier Analysis* ; Lower Extremity*

The purpose of this study was to investigate whether a radiographic estimate of osseous fractal dimension and power spectrum of 2D discrete Fourier transform is useful in the characterization of structural changes in bone. Ten specimens of bone were decalcified in fresh 50 ml solutions of 0.1 N hydrochloric acid solution at cummulative timed periods of 0 and 90 minutes, and radiographed from 0 degree projection angle controlled by intraoral parelleling device. I performed one-dimensional variance, fractal analysis of bony profiles and 2D discrete Fourier transform. The results of this study indicate that variance and fractal dimension of scan line pixel intensities decreased significantly in decalcified groups but Fourier spectral analysis didn't discriminate well between control and decalcified specimens.
Fourier Analysis* ; Fractals* ; Hydrochloric Acid ; Osteoporosis

PURPOSE: The purpose of this study was to evaluate the effect of the kV on fractal dimension of trabecular bone in digital radiographs. MATERIALS AND METHODS: 16 bone cores were obtained from patients who had taken partial resection of tibia due to accidents. Each bone core along with an aluminum step wedge was radiographed with an occlusal film at 0.08 sec and with the constant film-focus distance (32 cm). All radiographs were acquired at 60, 75, and 90 kV. A rectangular ROI was drawn at medial part, distal part, and the bone defect area of each bone core image according to each kV. The directional fractal dimension was measured using Fourier Transform spectrum, and the anisotropy was obtained using directional fractal dimension. The values were compared by the repeated measures ANOVA. RESULTS: The fractal dimensions increased along with kV increase (p<0.05). The anisotropy measurements did not show statistically significant difference according to kV change. The fractal dimensions of the bone defect areas of the bone cores have low values contrast to the non-defect areas of the bone cores. The anisotropy measurements of the bone defect areas were lower than those of the non-defect areas of the bone cores, but not statistically significant. CONCLUSION: Fractal analysis can notice a difference of a change of voltage of x-ray tube and bone defect or not. And anisotropy of a trabecular bone is coherent even with change of the voltage of x-ray tube or defecting off a part of bone.
Aluminum ; Anisotropy* ; Fourier Analysis ; Fractals* ; Humans ; Tibia

OBJECTIVE: Among various methods developed to quantitatively explore electroencephalograms (EEG), we focused on a wavelet method that was known to yield robust results under nonstationary conditions. The aim of this study was thus to introduce the wavelet method and demonstrate its potential use in clinical sleep studies. METHOD: This study involved artificial EEG specifically designed to validate the wavelet method. The method was performed to obtain time-dependent spectral power and phase angles of the signal. Synchrony of multichannel EEG was analyzed by an order parameter of the instantaneous phase. The standard methods, such as Fourier transformation and coherence, were also performed and compared with the wavelet method. The method was further validated with clinical EEG and ERP samples available as pilot studies at academic sleep centers. RESULT: The time-frequency plot and phase synchrony level obtained by the wavelet method clearly showed dynamic changes in the EEG waveforms artificially fabricated. When applied to clinical samples, the method successfully detected changes in spectral power across the sleep onset period and identified differences between the target and background ERP. CONCLUSION: Our results suggest that the wavelet method could be an alternative and/or complementary tool to the conventional Fourier method in quantifying and identifying EEG and ERP biomarkers robustly, especially when the signals were nonstationary in a short time scale (1-100 seconds).
Biomarkers ; Electroencephalography ; Fourier Analysis ; Pilot Projects

Five common electroretinograms and Fourier transform of the oscillatory potentials were recorded in adult diabetic patients with no observable retinopathy. To describe the limits of normal, we listed the median value, and actual values on either side of median that bracket 95% of the normal responses. In 68 of the 80 normal control eyes(85%), all ERG components were within normal limits. Only 52 of the 146 eyes in no diabetic retinopathy(35%) showed perfectly normal ERGs to our standard. The difference between the normal control eyes and diabetic eyes was statistically significant(p< 0.05 by Chi-square test). This fact may give proof that functional disturbance precedes the visible abnormalities of retina. A amplitude reduction of the second oscillatory potential and a timing delay of the maximal response a-wave were of frequent occurrences in diabetic patients with no retinopathy. The amplitude of the second oscillatory potential may be the best indicator reflecting erly retinal ischemic state, because a amplitude reduction attracts the examiners` eyes better than a timing delay.
Adult ; Fourier Analysis ; Humans ; Retina ; Retinaldehyde

The purpose of this study was to develop the respiratory training system using individual characteristic guiding waveform to reduce the impact of respiratory motion that causes artifact in radiotherapy. In order to evaluate the improvement of respiratory regularity, 5 volunteers were included and their respiratory signals were acquired using the in-house developed belt-type sensor. Respiratory training system needs 10 free breathing cycles of each volunteer to make individual characteristic guiding waveform based on Fourier series and it guides patient's next breathing. For each volunteer, free breathing and guided breathing which uses individual characteristic guiding waveform were performed to acquire the respiratory cycles for 3 min. The root mean square error (RMSE) was computed to analyze improvement of respiratory regularity in period and displacement. It was found that respiratory regularity was improved by using respiratory training system. RMSE of guided breathing decreased up to 40% in displacement and 76% in period compared with free breathing. In conclusion, since the guiding waveform was easy to follow for the volunteers, the respiratory regularity was significantly improved by using in-house developed respiratory training system. So it would be helpful to improve accuracy and efficiency during 4D-RT, 4D-CT.
Artifacts ; Displacement (Psychology) ; Fourier Analysis ; Respiration

An ECG signal, generally filled with noise, when de-noised, enables a physician to effectively determine and predict the condition and health of the heart. This paper aims to address the issue of denoising a noisy ECG signal using the Fast Fourier Transform based bandpass filter. Multi-stage adaptive peak detection is then applied to identify the R-peak in the QRS complex of the ECG signal. The result of test simulations using the MIT/BIH Arrhythmia database shows high sensitivity and positive predictivity (PP) of 99.98 and 99.96% respectively, confirming the accuracy and reliability of proposed algorithm for detecting R-peaks in the ECG signal.
Arrhythmias, Cardiac ; Electrocardiography ; Fourier Analysis ; Heart ; Noise